Conventionally, various types of inkjet recording apparatuses are used as image forming apparatuses including, for example, printers, facsimiles, and copiers. One of the types is a shuttle type inkjet recording apparatus which alternately repeats conveyance and recording for forming (recording) images on a recording medium; more specifically, with the shuttle type inkjet recording apparatus, a recording head for ejecting ink droplets (recording droplets) to a recording medium is serially traversed (scanning) in a direction perpendiculary intersecting a conveyance direction of the recording medium (also referred to as sheet, paper, or target recording medium), while the recording medium is intermittently conveyed according to recording area (width). Another type is a line type inkjet recording apparatus for increasing printing (recording) speed, in which the apparatus uses a line type recording head having a length equivalent to the recording width of the recording medium.
However, with the inkjet apparatuses, maintaining a constant distance between the recording medium and the recording head constant is difficult owing to factors such as warping of the recording medium or a roughness (irregularity) of the surface of the recording medium. In a case where the distance cannot be maintained constant, inconsistency in the distance occurs during a single scan or in one of the lines of a nozzle alignment, to thereby cause inconsistency in ejection time (flying time) of an ejected recording liquid. As a result, the landing area of the ejected recording liquid deviates from a target area. This deviation creates, for example, undesirable white lines and skewed thin lines, and adversely affects image quality.
In order to correct such warping or irregularity of the recording medium, various techniques are proposed for allowing a recording apparatus to convey a recording medium by absorbing the recording medium on a conveyor belt. In one example, a recording medium has its flatness maintained during conveyance by being absorbed to a conveyor belt with employment of electrostatic force. This reduces warping or irregularity of the recording medium during ejection of a recording liquid, thereby maintaining a constant distance between a nozzle and the recording medium.
However, with this technique using the conveyor belt, the conveyor belt may be stained by recording liquid when, for example, an unsteady movement occurs during a printing process. Further, in continuing such printing process where recording liquid is adhered to the conveyor belt, the recording liquid remaining on the conveyor belt may stain the recording medium, and/or may adversely affect the electrostatic absorption to cause conveyance error.
In order to solve the problems, a technique of employing a cleaning roller for removing recording liquid remaining on the conveyor belt, is proposed, for example, in Japanese Laid-Open Patent Application Nos. 7-53081 and 2000-263801.
Furthermore, a technique of employing a cleaning liquid along with the cleaning roller is proposed, for example, in Japanese Laid-Open Patent Application Nos. 11-192694, 2002-211060, and 2002-370416.
In another example shown in Japanese Laid-Open Patent Application No. 2002-249685 (although having an object different from preventing the recording liquid from staining the conveyor belt), a still picture display, which forms images by ejecting ink (recording liquid) onto a belt-like recording medium with use of an inkjet technique under a condition where the critical surface tension of the belt-like recording medium γc and the surface tension of the ink γL satisfy a relation of γc≦γL≦γc+5 dyne*cm−1, is proposed. With this example, ink can be prevented from blotting or repelled against the recording medium, and a satisfactory dot diameter can be obtained. This example, which is aimed not only to obtain satisfactory dot reproduction performance, but also to remove dried ink on the recording medium, solves the issue of removing dried ink by adding inorganic oxide materials or silicon emulsion.
As another example having a similar object, Japanese Laid-Open Patent Application No. 2002-249691 discloses a full color electronic blackboard, which forms images by ejecting ink (recording liquid) onto a belt-like recording medium with use of an inkjet technique under a condition where the critical surface tension of the belt-like recording medium γc and the surface tension of the ink γL satisfy a relation of γc≦γL≦γc+5 dyne*cm−1, and thus where the critical surface tension of the belt-like recording medium γc at 25° C. is set to 25-50 dyne*cm−1. Also with this example, ink can be prevented from blotting or repelled against the recording medium, and a satisfactory dot diameter can be obtained. This example is aimed not only to obtain satisfactory dot reproduction performance, but also to allow ink to satisfactorily fix to the recording medium, and to remove dried ink on the recording medium. In this example, the issue of fixing performance is solved by adding of a polymer.
With the conventional examples, however, recording liquid remaining on a conveyor belt could not be sufficiently removed since no consideration is made regarding the combination of the recording liquid and the conveyor belt.
Furthermore, the conventional apparatus employing the cleaning roller and the cleaning liquid requires, for example, a supplying apparatus for supplying the cleaning liquid, or a heating or blowing apparatus for drying the wetted conveyor belt. This leads to increase in size and cost of the apparatus.
Furthermore, the conventional still picture display or electronic blackboard cannot be suitably applied for removing recording liquid on a conveyor since ink removability is not considered from aspects of the critical surface tension of the recording medium or the surface tension of the recording liquid.